/Engine/Source/Runtime/Core/Public/Unix/UnixPlatformMemory.h
LLM uses these low level functions (LLMAlloc and LLMFree) to allocate memory. It grabs the function pointers by callingFPlatformMemory::GetLLMAllocFunctions. If these functions are not implemented GetLLMAllocFunctions should return false and LLM will be disabled.
static bool GetLLMAllocFunctions ( void *(*&)(size_t) OutAllocFunction, void(*&)(void *, size_t) OutFreeFunction, int32 & OutAlignment )